In the electro-smelting industry, with particular reference to the electrolytic smelting of aluminium, the production of anodes and cathodes often accounts for a large part of the operations and of the production cost of the final metal yield. An important process in the manufacture of anode and cathode carbons for such industries is the moulding of the socalled green blocks or electrodes which, after further processing -- particularly baking --, become the various types of anode carbons and cathode carbons required.
The paste compound which is used for producing anode and cathode carbons of this type usually consists, when required for the aluminium smelting industry, of pitch and petroleum coke as the main components, and this paste is tamped or compressed in a mould in order to produce the green electrodes which are subsequently subjected to a baking process.
A vibratory or shaking motion has for a long time been used for compacting the ingredients constituting the paste in a mould for forming the green electrodes. The equipment used for this vibrating process performs a key operation in the procedure for producing anode and cathode carbons. A number of strict demands are made of this vibratory equipment, which can be summarized as follows:
1. It must produce green electrodes of good quality for the subsequent baking operation, and for use in the smelting or electrolytic reduction process, i.e. blocks of high density. PA0 2. The equipment must be operationally reliable and as little prone as possible to faults or damage resulting from wear or other stresses. PA0 3. The costs of procuring, installing and operating the equipment must be as low as possible. PA0 4. Noise and vibration from the vibratory equipment to the surroundings must be reduced to the lowest possible level, so as to give an acceptable work environment, and also because of wear and other stresses on the equipment.
The type of equipment under discussion here has, for a number of years, been the object of a great many major and minor improvements and, almost up to the time of writing, numerous proposals for new ways of improving the process and the equipment used have been put forward. The technique which is standard usage to-day is thus the result of a long development, originating from the manual operation of pneumatic tamping (ramming) tools for compacting the paste in a mould. Using the manual method it was often found necessary to ram the paste into the mould, layer upon layer, in order to achieve the desired density throughout the entire body of the resultant block.
On account of the difficulty of obtaining adequate compaction throughout the whole of the block by ramming manually from above, it was considered necessary, on changing over to mechanized equipment, to make use of a shaking table, i.e. a vibrating base in the mould. All known equipment of this type has been based on vibration from below, and usually vibration of the bottom of the mould, or the mould table, and also of the vertical mould walls or sides.
One of the main reasons why experts in this field have assumed the vibration of the base or the table to be an unavoidable necessity in this connection, is probably that previous experience had shown that only the upper part of the paste was sufficiently compacted when worked from on top with manually manipulated tamping or ramming device.
As examples of the present state of the art, reference may be made to German Patent No. 1,758,297.4, which relates to complicated devices for the application of a vacuum in the vibrating or shaking process. French Patent No. 2,033,909 discloses a large number of different proposals aimed, inter alia, at furnishing equipment less liable to damage, fatigue failure and wear. In addition to the use of a vibratory table as base, it is also proposed to vibrate a cover plate over the paste which is to be compacted. The mould walls are supported independently of the vibratory table, and also independently of the cover plate. The device is thus of very complicated design, and comprises a large number of parts, with the result that it is difficult to achieve the stated objective because the larger the number of parts, the greater the likelihood of damage and faults occurring. Another significant problem is that the oscillatory system becomes very complicated and intricate.